Bird cage



FIG. 1 is a front view of a bird cage showing my new design;

FIG. 2 is a right side view thereof;

FIG. 3 is a left side view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a top plan view thereof; and,

FIG. 6 is a bottom view thereof. 

The ornamental design for a bird cage, as shown. 